Mediastinal irradiation, such as that used in the treatment of Hodgkin’s disease or breast cancer, may induce cardiac lesions namely constrictive pericarditis, restrictive cardiomyopathy, coronary artery disease, conduction disturbances, and/or valvular disease. The involvement of other thoracic organs and the presence of associated diseases such as pulmonary fibrosis and esophagitis are also typical in this scenario. The severity of the lesions depends upon the duration and the dosage of the radiation received. The evolution is progressive with almost always a latency period between the radiation and the cardiac manifestations.
Radiation may affect the aortic, mitral, or tricuspid valves. A significant number of patients present with involvement of several valves. The prevalence of valvular disease increases significantly in patients who have survived for more than 20 years following mediastinal irradiation.
On echocardiography, most patients present with type IIIa dysfunction with leaflet thickening and retraction ( Fig. 37-1 ). Subvalvular involvement is a common finding in the mitral and tricuspid positions. Valvular regurgitation with varying degrees of stenosis is present.
Results of histological examination show leaflet fibrosis with or without calcification in most instances. Calcifications are present at the level of the aortic valve and root, the aorto-mitral curtain, and the anterior leaflet of the mitral valve.
Patients with mild to moderate valvular disease should be followed closely to assess the progression of the disease and its potential impact on ventricular function. Patients with severe symptomatic valvular disease should be offered surgical therapy.
SURGICAL MANAGEMENT
The surgical strategy should take into consideration several characteristics specific to this population :
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A comprehensive cardiac work-up should be performed to identify all the valvular, cardiac, and extracardiac lesions.
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The evaluation of myocardial function is critical because most patients present with associated restrictive cardiomyopathy and diastolic dysfunction involving both the right and the left ventricles. Decreased cardiac output attributable to diastolic dysfunction despite a preserved ventricular ejection fraction is a strong negative predictor of outcome.
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Because of the increased risk of postoperative sternal necrosis that is directly correlated to the total dosage of radiation received, a surgical approach by thoracotomy should be preferred whenever feasible.
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All significant cardiac lesions amenable to surgical correction should be addressed during the same operation because a reoperative procedure is very challenging and carries a prohibitive risk. For example, patients with moderate aortic stenosis referred for mitral valve surgery or myocardial revascularization should undergo concomitant aortic valve replacement to avoid the risk of a second operation. A mechanical valve should be preferred to a valvular bioprosthesis, particularly in young patients. Mitral and tricuspid valve reconstruction can be performed if the leaflet tissue is not severely fibrotic, taking into consideration that the progression of fibrotic lesions is not predictable ( Fig. 37-2 ).
